MFC r220103:

MFC r220103:
  Normally fxp(4) does not receive bad frames but promiscuous mode
  makes controller to receive bad frames and i82557 will also receive
  bad frames since fxp(4) have to receive VLAN oversized frames. If
  fxp(4) encounter DMA overrun error, the received frame size would
  be 0 so the actual frame size after checksum field extraction the
  length would be negative(-2). Due to signed/unsigned comparison
  used in driver, frame length check did not work for DMA overrun
  frames. Correct this by casting it to int.
  While I'm here explicitly check DMA overrun error and discard the
  frame regardless of result of received frame length check.

  Reported by:	n_hibma
  Tested by:	n_hibma

git-svn-id: svn://svn.freebsd.org/base/stable/8@220342 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f